Physically unclonable functions (PUFs) rely upon a type of challenge-response authentication. A PUF may be embodied as a physical device or structure which is relatively easy to evaluate but difficult to predict. The response of a unique PUF device should be practically impossible to duplicate, even using the same process used to manufacture it. In this regard, a unique PUF device may be considered the hardware equivalent of a unique one-way function.
Rather than relying upon a single key, PUFs makes use of challenge-response authentication. When a stimulus is applied to the physical device or structure, it generates an unpredictable but repeatable response. The response may be due to the interaction of the stimulus with the physical microstructure of the device. In this context, the applied stimulus is called the challenge, and the reaction of the PUF to the stimulus is called the response. A challenge and its response together form a challenge-response pair. A challenge-response pair, once known, can be used to verify or authenticate a device, for example, or for other purposes.
The drawings illustrate only example embodiments and are therefore not to be considered limiting of the scope described herein, as other equally effective embodiments are within the scope and spirit of this disclosure. The elements and features shown in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the embodiments. Additionally, certain dimensions may be exaggerated to help visually convey certain principles. In the drawings, similar reference numerals between figures designate like or corresponding, but not necessarily the same, elements.